BARTOW COUNTY, Ga. -- Authorities say a generator was responsible for an explosion that injured four at Plant Bowen in Cartersville.

According to Georgia Power, the explosion occurred shortly after 4 p.m. on Thursday at Plant Bowen Unit 2 as the unit was coming down for a planned maintenance outage.

There are four power-generating units at the plant and the generator in question was the only one damaged.

The plant has been taken off-line while authorities investigate the explosion. A spokesperson from Georgia Power said there was "no ongoing threat" at Plant Bowen and it didn't expect the explosion to affect customers serviced by the plant.

All employees have been accounted for and the sole employee to be transported has since been released.

Witnesses nearby say the explosion sounded "louder than a sonic boom;" they say the explosion shook paintings off the walls.

The Bartow County Sheriff's Office has set up a phone line [706-226-9902] for people with family who may have been at Plant Bowen at the time of the explosion.